This invention relates to human-operated devices such as internal combustion engines. More particularly, this invention relates to a safety interlock that prevents the starting of such a device under certain conditions.
Safety switches are commonly used on many types of human-operated devices, including lawn and garden equipment such as lawnmowers. In a typical device having a safety interlock switch, the device cannot be operated unless the switch is actuated. In lawnmowers, the ignition system is either grounded or otherwise disabled if the safety switches are not in their proper positions.
For example, riding lawnmowers often have several safety switches, including a seat switch, a power take off (PTO) safety switch, and a transmission neutral switch. Before the engine will start, the seat switch must be closed indicating that the operator is sitting on the seat. Also, the PTO switch must be closed indicating that the PTO is disengaged. The transmission must also be in neutral to start the lawnmower, so that safety switch must also be closed.
Unfortunately, it may be possible to tamper with one or more of these safety switches by permanently closing it and thus deactivating it. For example, the seat switch could be taped shut to allow the engine to start even though the operator is not sitting on the seat. In such an event, it is possible for the device to operate even though a potentially hazardous condition exists.